DOKK / manpages / debian 10 / tcl8.6-doc / Tcl_GetStringResult.3tcl.en
Tcl_SetResult(3tcl) Tcl Library Procedures Tcl_SetResult(3tcl) 







Tcl_SetObjResult, Tcl_GetObjResult, Tcl_SetResult,
    Tcl_GetStringResult, Tcl_AppendResult, Tcl_AppendResultVA,
    Tcl_AppendElement, Tcl_ResetResult, Tcl_TransferResult, Tcl_FreeResult -
    manipulate Tcl result








#include <tcl.h>

Tcl_SetObjResult(interp, objPtr)

Tcl_Obj *
Tcl_GetObjResult(interp)

Tcl_SetResult(interp, result, freeProc)

const char *
Tcl_GetStringResult(interp)

Tcl_AppendResult(interp, result, result, ... , (char *) NULL)

Tcl_AppendResultVA(interp, argList)

Tcl_ResetResult(interp)

Tcl_TransferResult(sourceInterp, result, targetInterp)

Tcl_AppendElement(interp, element)

Tcl_FreeResult(interp)









  
Tcl_Interp *interp (out)

  
Interpreter whose result is to be modified or read.

  
Tcl_Obj *objPtr (in)

  
Tcl value to become result for interp.

  
char *result (in)

  
String value to become result for interp or to be appended to the
      existing result.

  
const char *element (in)

  
String value to append as a list element to the existing result of
      interp.

  
Tcl_FreeProc *freeProc (in)

  
Address of procedure to call to release storage at result, or
      TCL_STATIC, TCL_DYNAMIC, or TCL_VOLATILE.

  
va_list argList (in)

  
An argument list which must have been initialized using va_start,
      and cleared using va_end.

  
Tcl_Interp *sourceInterp (in)

  
Interpreter that the result and error information should be copied
    from.

  
Tcl_Interp *targetInterp (in)

  
Interpreter that the result and error information should be copied
    to.

  
int result (in)

  
If TCL_OK, only copy the result. If TCL_ERROR, copy the
      error information as well.
    
    

    

  










The procedures described here are utilities for manipulating the
    result value in a Tcl interpreter. The interpreter result may be either a
    Tcl value or a string. For example, Tcl_SetObjResult and
    Tcl_SetResult set the interpreter result to, respectively, a value
    and a string. Similarly, Tcl_GetObjResult and
    Tcl_GetStringResult return the interpreter result as a value and as a
    string. The procedures always keep the string and value forms of the
    interpreter result consistent. For example, if Tcl_SetObjResult is
    called to set the result to a value, then Tcl_GetStringResult is
    called, it will return the value's string representation.


Tcl_SetObjResult arranges for objPtr to be the
    result for interp, replacing any existing result. The result is left
    pointing to the value referenced by objPtr. objPtr's reference
    count is incremented since there is now a new reference to it from
    interp. The reference count for any old result value is decremented
    and the old result value is freed if no references to it remain.


Tcl_GetObjResult returns the result for interp as a
    value. The value's reference count is not incremented; if the caller needs
    to retain a long-term pointer to the value they should use
    Tcl_IncrRefCount to increment its reference count in order to keep it
    from being freed too early or accidentally changed.


Tcl_SetResult arranges for result to be the result
    for the current Tcl command in interp, replacing any existing result.
    The freeProc argument specifies how to manage the storage for the
    result argument; it is discussed in the section THE TCL_FREEPROC
    ARGUMENT TO TCL_SETRESULT below. If result is NULL, then
    freeProc is ignored and Tcl_SetResult re-initializes
    interp's result to point to an empty string.


Tcl_GetStringResult returns the result for interp as
    a string. If the result was set to a value by a Tcl_SetObjResult
    call, the value form will be converted to a string and returned. If the
    value's string representation contains null bytes, this conversion will lose
    information. For this reason, programmers are encouraged to write their code
    to use the new value API procedures and to call Tcl_GetObjResult
    instead.


Tcl_ResetResult clears the result for interp and
    leaves the result in its normal empty initialized state. If the result is a
    value, its reference count is decremented and the result is left pointing to
    an unshared value representing an empty string. If the result is a
    dynamically allocated string, its memory is free*d and the result is left as
    a empty string. Tcl_ResetResult also clears the error state managed
    by Tcl_AddErrorInfo, Tcl_AddObjErrorInfo, and
    Tcl_SetErrorCode.


Tcl_AppendResult makes it easy to build up Tcl results in
    pieces. It takes each of its result arguments and appends them in
    order to the current result associated with interp. If the result is
    in its initialized empty state (e.g. a command procedure was just invoked or
    Tcl_ResetResult was just called), then Tcl_AppendResult sets
    the result to the concatenation of its result arguments.
    Tcl_AppendResult may be called repeatedly as additional pieces of the
    result are produced. Tcl_AppendResult takes care of all the storage
    management issues associated with managing interp's result, such as
    allocating a larger result area if necessary. It also manages conversion to
    and from the result field of the interp so as to handle
    backward-compatibility with old-style extensions. Any number of
    result arguments may be passed in a single call; the last argument in
    the list must be a NULL pointer.


Tcl_AppendResultVA is the same as Tcl_AppendResult
    except that instead of taking a variable number of arguments it takes an
    argument list.


Tcl_TransferResult moves a result from one interpreter to
    another, optionally (dependent on the result parameter) including the
    error information dictionary as well. The interpreters must be in the same
    thread. The source interpreter will have its result reset by this
  operation.












Use of the following procedures is deprecated since they
    manipulate the Tcl result as a string. Procedures such as
    Tcl_SetObjResult that manipulate the result as a value can be
    significantly more efficient.


Tcl_AppendElement is similar to Tcl_AppendResult in
    that it allows results to be built up in pieces. However,
    Tcl_AppendElement takes only a single element argument and it
    appends that argument to the current result as a proper Tcl list element.
    Tcl_AppendElement adds backslashes or braces if necessary to ensure
    that interp's result can be parsed as a list and that element
    will be extracted as a single element. Under normal conditions,
    Tcl_AppendElement will add a space character to interp's
    result just before adding the new list element, so that the list elements in
    the result are properly separated. However if the new list element is the
    first in a list or sub-list (i.e. interp's current result is empty,
    or consists of the single character “{”, or ends in the
    characters “ {”) then no space is added.


Tcl_FreeResult performs part of the work of
    Tcl_ResetResult. It frees up the memory associated with
    interp's result. It also sets interp->freeProc to zero, but
    does not change interp->result or clear error state.
    Tcl_FreeResult is most commonly used when a procedure is about to
    replace one result value with another.








It used to be legal for programs to directly read and write
    interp->result to manipulate the interpreter result. The Tcl
    headers no longer permit this access by default, and C code still doing this
    must be updated to use supported routines Tcl_GetObjResult,
    Tcl_GetStringResult, Tcl_SetObjResult, and
    Tcl_SetResult. As a migration aid, access can be restored with the
    compiler directive




#define USE_INTERP_RESULT



but this is meant only to offer life support to otherwise dead code.









Tcl_SetResult's freeProc argument specifies how the
    Tcl system is to manage the storage for the result argument. If
    Tcl_SetResult or Tcl_SetObjResult are called at a time when
    interp holds a string result, they do whatever is necessary to
    dispose of the old string result (see the Tcl_Interp manual entry for
    details on this).


If freeProc is TCL_STATIC it means that
    result refers to an area of static storage that is guaranteed not to
    be modified until at least the next call to Tcl_Eval. If
    freeProc is TCL_DYNAMIC it means that result was
    allocated with a call to Tcl_Alloc and is now the property of the Tcl
    system. Tcl_SetResult will arrange for the string's storage to be
    released by calling Tcl_Free when it is no longer needed. If
    freeProc is TCL_VOLATILE it means that result points to
    an area of memory that is likely to be overwritten when Tcl_SetResult
    returns (e.g. it points to something in a stack frame). In this case
    Tcl_SetResult will make a copy of the string in dynamically allocated
    storage and arrange for the copy to be the result for the current Tcl
    command.


If freeProc is not one of the values TCL_STATIC,
    TCL_DYNAMIC, and TCL_VOLATILE, then it is the address of a
    procedure that Tcl should call to free the string. This allows applications
    to use non-standard storage allocators. When Tcl no longer needs the storage
    for the string, it will call freeProc. FreeProc should have
    arguments and result that match the type Tcl_FreeProc:






typedef void Tcl_FreeProc(


        char *blockPtr);




When freeProc is called, its blockPtr will be set to
    the value of result passed to Tcl_SetResult.








Tcl_AddErrorInfo, Tcl_CreateObjCommand, Tcl_SetErrorCode,
    Tcl_Interp








append, command, element, list, value, result, return value,
    interpreter







  

    8.0
    Tcl